更新

HttpClientStudy.Core/CustomHttpClient/TokenDelegatingHandler.cs

@@ -19,7 +19,7 @@ namespace HttpClientStudy.Core.CustomHttpClient
 
             if (request.Headers.Authorization is null) 
             {
-                request.Headers.Add(HeaderNames.Accept, "Bearer " + "a.b.c");
+                request.Headers.Add(HeaderNames.Authorization, "Bearer " + "a.b.c");
             }
 
             HttpResponseMessage response = base.Send(request, cancellationToken);

HttpClientStudy.Core/HttpClientStudy.Core.csproj

@@ -9,6 +9,7 @@
   <ItemGroup>
     <PackageReference Include="Microsoft.Extensions.Http" Version="8.0.0" />
     <PackageReference Include="Microsoft.Extensions.Http.Polly" Version="8.0.1" />
+    <PackageReference Include="Microsoft.Net.Http.Headers" Version="8.0.7" />
     <PackageReference Include="Polly" Version="8.2.1" />
     <PackageReference Include="Polly.Caching.IDistributedCache" Version="1.0.4" />
     <PackageReference Include="Polly.Extensions.Http" Version="3.0.0" />